One of the world’s most prestigious science labs – CERN – has found that cosmic rays affect cloud formation.

By way of background, the news magazine for the prestigious science journal Nature noted yesterday:

The number of cosmic rays that reach Earth depends on the Sun. When the Sun is emitting lots of radiation, its magnetic field shields the planet from cosmic rays. During periods of low solar activity, more cosmic rays reach Earth.

Scientists agree on these basic facts, but there is far less agreement on whether cosmic rays can have a large role in cloud formation and climate change. Since the late 1990s, some have suggested that when high solar activity lowers levels of cosmic rays, that in turn reduces cloud cover and warms the planet. Others say that there is no statistical evidence for such an effect.

The Director of CERN’s cosmic ray experiment (Jasper Kirby) now says that experiments show that cosmic rays significantly enhance the production of the particles which initiate the cloud-formation process. Specifically, cosmic rays allow the minute amounts of sulfuric acid and ammonia in the atmosphere to stabilize, and then – when the clusters grow to 20 molecules or more – become the structure around which moisture can condense so that clouds begin to form.

The CLOUD results show that trace vapours assumed until now to account for aerosol formation in the lower atmosphere can explain only a tiny fraction of the observed atmospheric aerosol production. The results also show that ionisation from cosmic rays significantly enhances aerosol formation.

A new scientific paper published today by the CERN team in Nature summarizes the results. And here is a chart graphically conveying the results of the experiment:

While the CERN findings are very important, they are not the first experimental results to confirm the affect of cosmic rays on cloud formation.

A team of Danish scientists from Aarhus University and the National Space Institute published results in May showing the same basic mechanism:

[Danish scientists] have directly demonstrated in a new experiment that cosmic radiation can create small floating particles – so-called aerosols – in the atmosphere. By doing so, they substantiate the connection between the Sun’s magnetic activity and the Earth’s climate.

With the new results just published in the recognised journal Geophysical Research Letters, scientists have succeeded for the first time in directly observing that the electrically charged particles coming from space and hitting the atmosphere at high speed contribute to creating the aerosols that are the prerequisites for cloud formation.

The more cloud cover occurring around the world, the lower the global temperature – and vice versa when there are fewer clouds. The number of particles from space vary from year to year – partly controlled by solar activity. An understanding of the impact of cosmic particles – consisting of electrons, protons and other charged particles – on cloud formation and thereby the number of clouds, is therefore very important as regards climate models.

With the researchers’ new knowledge, it is now clear that here is a correlation between the Sun’s varying activity and the formation of aerosols in the Earth’s atmosphere.

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In a climate chamber at Aarhus University, scientists have created conditions similar to the atmosphere at the height where low clouds are formed. By irradiating this artificial atmosphere with fast electrons from ASTRID – Denmark’s largest particle accelerator – they have also created conditions that resemble natural ones on this point.

Simply by comparing situations in the climate chamber with and without electron radiation, the researchers can directly see that increased radiation leads to more aerosols.

In the atmosphere, these aerosols grow into actual cloud nuclei in the course of hours or days, and water vapour concentrates on these, thus forming the small droplets the clouds consist of.